Over the past several years, scientists have looked deeper into how brains age and confirmed that they continue to develop through and beyond middle age.

Many longheld views, including the one that 40 percent of brain cells are lost, have been overturned. What is stuffed into your head may not have vanished but has simply been squirreled away in the folds of your neurons.

One explanation for how this occurs comes from Deborah M. Burke, a professor of psychology at Pomona College in California. Dr. Burke has done research on “tots,” those tip-of-the-tongue times when you know something but can’t quite call it to mind. Dr. Burke’s research shows that such incidents increase in part because neural connections, which receive, process and transmit information, can weaken with disuse or age.

But she also finds that if you are primed with sounds that are close to those you’re trying to remember — say someone talks about cherry pits as you try to recall Brad Pitt’s name — suddenly the lost name will pop into mind. The similarity in sounds can jump-start a limp brain connection. (It also sometimes works to silently run through the alphabet until landing on the first letter of the wayward word.)

That’s a wonderful technique, all the more so because it sounds like something Cicero might have invented.

We are born with a highly structured brain. But those brains are also transformed by our experiences, especially our early experiences. More than any other animal, we humans constantly reshape our environment. We also have an exceptionally long childhood and especially plastic young brains. Each new generation of children grows up in the new environment its parents have created, and each generation of brains becomes wired in a different way. The human mind can change radically in just a few generations.

These changes are especially vivid for 21st-century readers. At this very moment, if you are under 30, you are much more likely to be moving your eyes across a screen than a page. And you may be simultaneously clicking a hyperlink to the last “Colbert Report,” I.M.-ing with friends and Skyping with your sweetheart.

We are seeing a new generation of plastic baby brains reshaped by the new digital environment. Boomer hippies listened to Pink Floyd as they struggled to create interactive computer graphics. Their Generation Y children grew up with those graphics as second nature, as much a part of their early experience as language or print. There is every reason to think that their brains will be as strikingly different as the reading brain is from the illiterate one.

Should this inspire grief, or hope? Socrates feared that reading would undermine interactive dialogue. And, of course, he was right, reading is different from talking. The ancient media of speech and song and theater were radically reshaped by writing, though they were never entirely supplanted, a comfort perhaps to those of us who still thrill to the smell of a library.

But the dance through time between old brains and new ones, parents and children, tradition and innovation, is itself a deep part of human nature, perhaps the deepest part. It has its tragic side. Orpheus watched the beloved dead slide irretrievably into the past. We parents have to watch our children glide irretrievably into a future we can never reach ourselves. But, surely, in the end, the story of the reading, learning, hyperlinking, endlessly rewiring brain is more hopeful than sad.

Put these two together, and you get a picture that’s even more hopeful. Our brains aren’t just plastic over the span of human evolution or historical epochs, but over individual lives. It might be easier and feel more natural for children, whose brains seem to us to be nothing but plasticity. But we don’t just have a long childhood — to a certain extent, our childhood never ends.

Human beings are among the only species on the planet who evolved to thrive in any kind of climate and terrain on the planet. (Seriously; underwater is the only real exception.) Compared to that, summoning the plasticity required to engage with any new kind of media is a piece of cake.

Good list. And Gopnik of course has done great work on children and adolescents, especially in her The Philosophical Baby.

Jonah Lehrer also has a wonderful blog, The Frontal Cortex, which I never stop telling people about whenever I can. It’s better than the books, even — no need for narrative juxtapositions or slow reveals.